Centralized traffic controlling system for railroads



Aug. 9,1938. N. D. PRESTON CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Original Filed May 24, 1933 3 Sheets-Sheet 1 INVENTOR mam o wzou Q Aug. 9, 1938. N. D. PRESTON CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 3 Sheets-Sheet 2 Original Filed May 24, 1933 Patented Aug. 9, 1938 PATENT OFFICE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Neil D. Preston, Rochester, N. Y., assignor to General Railway Signal Company,

Rochester,

Application my 24, 1933, Serial No. 672,652

, Renewed January 3, 1938 13 Claims.

This invention relates to systems for governing trafiic on railroads and it more particularly pertains to systems known as centralized trafiic controlling systems.

In a centralized trailic controlling system of the type contemplated by this invention, communica-- tion is established between a central control oflice and a number of outlying field stations by means of a station selective coded type of communication system. In a communication system of this type, a plurality of series of impulses of different'c'ode combinations are transmitted over the line circult connecting the control office andthefield stations. The first portion of each different series of code combinations is employed for selecting the stations, while the later portion of'eacn diirerent series of code combinations is employed to control the traflic controlling devices at the selected station. I 1

A centralized trailic controlling system in which the present invention is useful, has the switches and signals at various stations along a railroad system placed under the control of an operator in the control office in such a way that he may change the positions of the switches, subject to automatic approach and detector locking circuits which prevent unsafe operation of any switch. He may also hold any of the signals at stop or allow them to clear, dependent upon the positions of the associated switches and also provided the location of trains makes it safe for a signal to indicate proceed.

In a centralized traflic controlling system of the type contemplated by this invention, various indications are displayed in the control office to indicate the presence or absence of'trains on the various track sections and to indicate the operated positions of the various switches,sign als andthe like.

In a system as above outlined, the various switches and signals at the'passing siding's or the like which are distributed throughout the territory are grouped in what may be conveniently termed field stations, which usually include those traffic controlling devices located near or ad jacent each other. The communication system which interconnects the control oilice with the various field stations for the transmission of controls and indications is preferably of the coded duplex type, as disclosed for example in the pending application of Judge and Bushnell, Ser. No. 640,062 filed October 28, 1932, corresponding to British Patent 419,399, A communication system of this type is operable'through cycles of operation during which a code call'is transmitted for the selection of the desired station, after which the controls are transmitted to the individual traffic controlling devices atthat station.

Since the present inventionis particularly directed to the transmission of outbound controls and since the'oper'ation of, the system in connec- Where the number of switches and signals in a track layout at one location is more than can be conveniently controlled in one operating cycle, it becomes necessary to provide some means to prevent clearing signals over wrong routes. For ex ample, referring to the typical arrangement of two switches shown in Fig. 3 and assuming that switch ITS is in its reverse position, switch 2TS is in its normal position and that the operator desires to clear the route over both switches reversed. Under these conditions, if a control code is transmitted to clear signal IAE, this signal may show clear before switch ZTS- is reversed thereby displaying the wrong route indication." A feature of the present invention contemplates checking the reception of switch controls before permitting clearing of signals.

In the present invention, it is proposed to arrange a portion of the cycle for the transmission of a message indicating whether or not a switch lever in the control oiTlce has been shifted to a new position so that transmission, proper execution and registration of the switch controls must occur before a signal can clear. More specifically, if a switch lever has been moved to a new posi-- tion, one cycle of operations is effective to select a particular field station and to transmit a code combination for preparing the proper signal clearing circuit at the selected station. Thereafter an additional cycle is effective for controlling the switches at the selectedstation and for completing the signal clearing circuit.

In many cases the signals may be cleared over a particular route without operating any of the switches to new positions. In this event it is undesirable to transmit a cycle for controlling switches and a further feature of the present invention contemplates the operation of the system through only one operating cycle if signals are to be cleared without the operation of any switch or switches. Such an operating cycle is eifective to transmit signal controls alone.

These characteristic features of the invention thus briefly stated will be explained more in detail in the following description of one embodiment and the various functions and advantages of a system employing this invention will be in part pointed out and in part apparent as the description progresses.

In the accompanying drawings, the invention has been shown applied to a track layout at a single location having two track switches and associated signals but it should be understood that, H the invention is not limited as thus shown, since it may be readily applied to all types and combinations of track layouts.

In describing the invention in detail, reference will be made to the accompanying drawings in which similar parts throughout the several views are designated by similar reference characters, some of which are provided with distinctive exponents to indicate the location of the associated apparatus in the system and some of which are provided with distinctive ordinals to indicate the order of operation of the particular device with which the reference character is associated and in which:-

Fig. 1 illustrates the apparatus and circuit arrangement provided as a portion of a typical control ofiice equipment constructed and arranged according to the present invention.

Figs. 2 and 3 when placed end to end, illustrate the apparatus and circuit arrangement employed at a typical field station for providing the control of a plurality of track switches and signals at a single location in accordance with the present invention and adapted to be associated with the apparatus employed in the control ofiice.

In considering the detailed operation of the system employed in the embodiment of the present invention, Fig. 1, Fig. 2 and Fig. 3 should be placed end to end in the order named with corre spondingly numbered lines in alignment.

For the purpose of simplifying the illustrations and facilitating in the explanation, the various parts and circuits have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose of enabling a clear understanding of the principles and mode of operation to be obtained, rather than with the idea of illustrating the specific construction and arrangement of parts that would be actually em ployed in practice. The various relays and their contacts are illustrated in a conventional manner and symbols are used to indicate the connections to the terminals of batteries or other suitable sources of current, instead of showing all of the wiring connections to these terminals.

The symbols and indicate the positive and negative terminals respectively of suitable batteries or other sources of direct current and the circuits with which these symbols are used always have current flowing in the same direction. The symbols (B+) and (B) indicate connections to the opposite terminals of a suitable battery or other direct current source which has an intermediate tap (CN) and the circuitswith which these symbols are used may have current flowing in one direction or the other,

depending upon the particular terminal used in combination with the intermediate tap (CN).

Communication system in generaZ.For the transmission of controls, a transmitting equipment is located in the control office and a receiving equipment is located at each of the various field stations. These receiving equipments are connected to the transmitting equipment by a suitable communicationline circuit comprising a control line and a return line. In the drawings, the control line is identified by the reference character I0 and the return line by the reference character I2. The control line circuit is used for the transmission of impulses from the conposition of a switch machine lever.

trol oflice and includes a three-position polarized biased-to-neutral line relay F in the control ofiice and a similar relay F at each field station.

The transmission of a series of distinctive impulses over the control line circuit results in the synchronous step-by-step operation of a stepping relay bank at the control oifice and at each field station, irrespective of the polarity of the impulses. The polarity of the impulses determines the particular. field station to be selected during the first part of the operating cycle, while the polarity of the impulses during the later part of the operating cycle determines the controls to be transmitted to the selected field station.

For the transmission of indications to the control ofiice, only one field station at a time is permitted to transmit over the indication line cir-' cuit during any particular operating cycle as determined by some suitable lock-out arrangement. This selection of a field station for permitting it-to transmit indications is immaterial for an understanding of the present invention and therefore has been omitted.

Control ojfice equipment-The control ofiice (see Fig. 1) includes a control machine having a group of control levers for'each field station, together with suitable apparatus and circuits to accomplish proper functioning of the system. Fig. 1 illustrates diagrammatically only a portion of such a control machine, which is typical of the apparatus associated with a track section comprising two track switches as illustrated in the upper right hand portion of Fig. 3.

The apparatus for the two track switches comprises switch machine control levers ISML and ZSML, a signal control lever SGL and a self-restoring starting button SB. The movement of a switch machine control lever to one extreme position or the other results in the normal or reverse operation of the corresponding track switch at the corresponding field station through the medium of the communication system. The movement of the signal control lever from its intermediate or full line position shown in Fig. l (which corresponds to signals at-stop) to the right or left dotted positions clears a signal for trafiic over the associated track switch in an eastbound or a westbound direction respectively, through the medium of the communication system.

The movement of the signal control lever and the subsequent operation of the associated starting button without the movement of an associated switch machine lever, results in a single cycle of operations of the communication system, during which a code combination of one class is transmitted and the signal is cleared at the end of the cycle. If one or both of the switch machine levers is actuated and the signal lever is positioned to clear a signal, followed by the operation of the starting button, then the code combination is transmitted to the selected field station for preparing the signal clearing circuit during a first cycle of the communication system. No switch machine control is transmitted during this first cycle under this condition, but the system goes through a second cycle during which the transmission of a code combination of another class takes place which includes switch controls. The signal clearing circuit is completed at the end of the second cycle.

Checking relay WCK, normally energized over its stick circuit, is dropped when a cycle is initiated during which switch controls are to be transmitted as determined by a change in the Signal change or starting relay SGCH picks up "when the associated starting button is actuated and stores. the condition that the associated station is to be selected. Switchchange or starting relay SMCI-I is picked up to store the condition that a lever has been moved from one position to another. In other words, these two starting relays when picked up cause the communication system to go through cycles of operations, only one cycle being effected if relay SGCH is picked up alone, while two cycles are effected if "both relays SGCH and SMCH are picked up to initiate the system.

Signal code determining relay S'GCD and switch machinecode determining relay SMCD associated with a particular field station are controlled by their respective change relays in such a way that the signal code determining relay determines the code combination which is transmitted during the first cycle and the switch machine code determining relay determines the combination which is transmitted during the second cycle. The interlocking circuits of these two relays are such that only one of them can be picked up at any onetime, with relay SGCD having preference. Relays EP, FP, ZFP, SA, ZSA, PC, NC and C correspond to similar relays in the above mentioned prior application Ser. No. 640,062 and since the operation of these relays, as well as the operation of the stepping relay bank, has been thoroughly explained in this prior application, a detailed description of their functioning will not be given here.

The control office equipment also includes a line battery CB for supplying positive and negative potential to the line circuit in accordance with the positions of positive control relay PC and negative control relay NC.

Field station equipment-With reference to the typical field station equipment shown in Figs. 2 and 3, two turn-out tracks have "been shown controlled by means of track switches ITS and 2T8. These track switches are suitably controlled from one extreme position to the other by suitable switch machines (not shown) such for example, as in the patent to W. K. Howe, No. 1,466,903 dated September 4, 1923. These switch machines are in turn controlled by switch ma-- chine relays lS-MR and ZSMR, subject to suitable approach locking means and since the detailed circuit arrangements for this control is immaterial to an understanding of the present inven tion, the: control of the track switches through the medium of the switch machines has been merely indicated by means of dotted lines extending from the contacts of the switch machine relays to their associated track switches.

The positions of the track switches are indicated by the usual switch repeating relays llWP and ZWP which are of the polar neutral type, energized with a particular polarity so that their polar contacts are positioned to the right when the associated switch machine is in its normally locked position and to the left when the corresponding switch machine is in its reverse locked position. The neutral contacts of these relays drop to their deenergized positions when the cor-' responding switch is unlocked or is in operation. These switch repeating relays are likewise indicated as being controlled from the corresponding track switches by means of dotted line connections instead of showing the detail-ed circuit artransmission of switch controls.

nals *I-E and lilE govern e'a'stbound trafiic over the track switch 'ITS over the main track and onto the turn-out track respectively. Signal IW governs west-bound trafiic over the main track, signal IAW governs westbound traffic 'over the center track onto the main. track and signal -|BW governs 'trafiic-overthe upper track onto the main track by way of the center track.

Each signal is associated with a signal control relay, for example, the signal-control relays IEG and -IAEG clear signals lE and IAE respectively when these relays are picked up and when they are dropped *the corresponding signals 'are put to stop. Likewise, relays :IWG, IAWG and IBWG clear signals IW, 1 AW and lBW respectively when these relays are picked up and the respective signals are put to stop when the corresponding relays are dropped.

The signal control relays IEG, IAEG, IWG, I AWG and 'IBWG are governed from the control office through the medium of the communication system. Each signal relay is dependent forits energization upon the traflic direction relay TD being properlypositioned, as well as proper correspondence between the switch relays and the switch machine repeating relays.

When all of the signals are at stop, relay M is energized through a circuit which includes back contacts on each of the signal control relays. Checking relay CK, normally energized by means of its stick circuit, permits clearing of signals during a cycle for the transmission of signals alone. I his relay is dropped during a signal control cycle if this cycle is to be followed by a switch control cycle,- so that clearing of signals is prevented in this case until the proper switch controls have been transmitted.

Clearing relay CL is for the purposeof energizing the signal clearing circuit and when this relay is picked up it is stuck up until the associated track section becomes occupied or until a stop signal code is transmitted for picking up stop relay SP. Signal station relay SGST and switch machine station relay SMST correspond to the signal code determining and switch machine code determining relays respectively in the control office, since relay SGST is picked up during a cycle for the transmission of signal controls and relay SMST is picked up during a cycle for the Code receiving relays IPC, 2PC and 3P0 record the positive impulses applied to the control line and code receiving relays INC, 2N0 and 3NC record the negative impulses applied to the control line, these relays being selected on the first three steps after station selection by means of stepping relays 3V 4V and 5V These code receiving relays record the polarity of the code impulses and by means.

of circuits made up through their contacts, proper selection is made of the various control relays, all of which will be pointed out in the detailed description.

Executing relay EX is picked up on the sixth step, which step follows the registration of the code which positions the code receiving relays. Relay EX controls certain detailed executing circuits as will be more clearly explained in connection with the detailed description.

Relays FP SA and the stepping relays correspond to similar relays in the above mentioned prior application Ser. No. 640,062 and since the operation of these relays may be the same as disclosed in this prior application, a detailed discussion relating to this portion of the system will not be given here.

It is to be understood that although the field station has not been shown as having indication transmitting means nor has the control oflice been shown as having indication receiving means, a complete system as contemplated to be employed in accordance with the present invention would have such features. However, for the purpose of describing the present invention, such features are considered as immaterial.

It is believed that the nature of the invention, its advantages and characteristic features can be best understood with further description being set forth from the standpoint of operation.

Operation The system is normally at rest but may be initiated by the operator for the transmission of controls in the manner fully set forth in the above mentioned prior application, Ser. No. 640,062. Front contact 21 on relay SGCH of Fig. 1 corresponds to front contact 21 on relay ICI-I of Fig. 5 in the above mentioned prior application and since front contact 28 on relay SMCI-I of Fig. 1 is in multiple with front contact 21, the picking up of either one or both relays SGCH and SMCI-I initiates the system. 7

It will be assumed that the system steps through cycles of operations as long as one of these change relays is picked up and an explanation will be given of the features and operation of the present embodiment which more particularly pertains to the transmission of controls to a selected station after the station selecting steps have been marked oil. In this connection, it is assumed that the station illustrated in Figs. 2 and 3 is selected on the first two steps of the cycle and that the third, fourth, fifth and sixth steps are employed for the transmission of the code combinations to the selected station.

With the possibility of having either a positive or a negative impulse for each step of the communication system, the number of code combinations is equal to'two (2) raised to the power of the number of steps. In the present illustration, three steps have been employed for the route control codes and with the impulses for these three steps arranged in code combinations, eight different codes are used, two of which are in the group of combinations conveniently referred to as of the first class, that is, where the communication system steps through only one cycle of operations. The remaining six code combinations are conveniently referred to as of the second class, in which the communication system steps through two cycles of operation for each code combination.

By referring to the table given below, it will be noted that the first code (third step) is always for the first cycle and for the second cycle. The second code (fourth step) is for the combinations of the first class, as determined in the control office by the fact that no switch machine lever is moved to a new position and repeated at the field station by maintaining the checking relay in its picked up position. The second code of the first cycle is when a switch machine lever is moved to a new position requiring the transmission of a second series of impulses. The third code (fifth step) is or for the first cycle as determined by the direction of trafilc to be cleared at the field station.

The second code (fourth step) of the second cycle is or as determined by switch machine lever ISML in its normal position or its reverse position respectively. The third code impulse (fifth step) of the second cycle is or as determined by switch machine lever ZSML being in its normal position or its reverse position respectively.

Table of code combinations (first class) Code number Fourth step Fifth step Third Step Code use Code number No switch lever changed. Clear signal east. N 0 switch lever changed. Clear signal west.

Table of code combinations (second class) Fifth step Fourth step Third Step Code use 1. lst cycle.

2nd cycle 2. 1st cycle 2nd cycle 3. 1st cycle 2nd cycle 4. lst cycle 2nd cycle 5. 1st cycle 2nd cycle 6. 1st cycle 2nd cycle Switch lever changed.

Select signal east.

Position switch No. 1 normal. Clear signal east.

Switch lever changed.

Select signal west.

Position switch N o. 1 normal. Clear signal west.

Switch lever changed. Select signal west. Position switch No.

(No. 2 normal). Clear signal west.

Switch lever changed. Select signal east. Position switch No.

(N o. 2 reverse). Clear signal east.

Switch lever changed. Select signal west. Position switch N o.

(No. 2 reverse). Clear signal west.

1 reverse 1 reverse 1 rever Station selection andLsiep-byastep operation.- At the beginning of thecycler relay FF is energized by polar contact 61: in; either: a right or a left hand position, dependingupon the polarity with. which line Ill is energized. The closure of front contact 68 of relay"FP energizes relay ZFP which in turn. energizes the slow acting relay SA by closing front contact 69. Relay SA picks up after a short time. intervali and closes a circuit by way of its front contact 'lll for picking. up relay 2SA.. Rielays SA; and. ZSA. remain picked up throughout the cycle ofloperations until a predetermined period ofntime after the" control line has been deenergized at the end. of

the: cycle. I

.Relays F FP SA and S at t'he. field station are picked up at the beginning of the cycle; Relay FP repeatsthe impulses in. the. line circuit irrespective of theirzpolarity while relay F is positioned to the rightiby. a: impulse. and to the left by a impulse. Relay S0 remains picked up at thevselected station until the end of the cycle and. relay SA remains pickedup until a. predetermined period. of time after the. control line-has been deenergized at the end of the cycle. e

Upon the first deenergizationx of the. control line (following its first" energizationo as repeated by relays FF and FF, the first stepping relay is picked up and. similarly, during each following deenergized condition: of'the: control line av su'c ceeding steppingrelay isipicked: um, so P that. after the station hasubeen selected by the continued energization. of relay $0 the. control steps are then taken. which. include. stepping; relays 3M 4V 5V and 6V atthe selectedlstation; It will be understood that relays SGGD andtSMGD have multiple sets of contacts: soithat either onepicked up, controls; stationselection. during: the? first steps .of the cycle intthe same ma-nner that relay ICD controls the. selection of. a. station in the above mentioned; prior application" Ser. No. 640,062.; 1

Single signal clearing cycZe.-Itwill now be assumedthat the operator: desires toiclear signal l-Exfor traffic over the .main: track in an eastwardtdirectionz (see Eig'. 3);: Since; switch machine levers lSMLand12SlVlL are inv their normal positions, trackswitch'esa ITS; and 2TB :wilLbe as sumed' to be inxtheirno'rmal' positions. In this event; it is: not necessary to-operate? a switch machine lever so that; the operation of signal lever SGLto its-right dottede'linel'position i'seflfective to transmit. a. code for-nclearing signal.- IE I on a single. cycle.

After lever. SGIi .ismovedto its. right position, the starting button SBis actuated which closes a circuit for picking up relay SGCHi which ex tends from. 0+) front contact: H of button SB and winding of relay SGCH,1to Relay SGCH: closes a stick circuit for itself. extending from? back contact: l31of rielaySGCD; front contact. 14 and" winding of? relay SGCH, to The closing of front: contact 2]! initiates'zthe cycle of: operations as above noted;

A circuit is closed for picking uprelay SGCD extending from back: contact l5of relay.

SA, backzcontact. liiiof relay NC, .backcontact ll: of relay PCrfrontn contact. 181 of relay SGGH' and winding of relay SGCD, .to(). The. openingof backcontact l8 of relayv SGCI-Iprevents the energizationof any other GD. relay, includ= ing relay SMCD in the chain. circuit; n the; event that another change. relay. is; picked. up 1 such as relay SMCH.

the series but farther along In other words, if two or more change relays are up at the same time; the signalcode determining relay such-as relay SGCD nearest the end of the circuit including conductor l9 has-preference;

I he picking up= of relay SGClD closes a stick circuit for itself extending from back contact 2B- of relay 2SA, back contact 21 of relay SMCD, front contact 22 and winding of relay SGCD, to: Since relay SA is picked up before: relay ZSA this stick circuit is maintained energized through front contact 2'3. of relay SA after the picking up of relay 28A, so that relay SGCD remains stuck up until: the end of the cycle. Since relay SA is dropped before relay 2SA at the end of the. cycle, this stick circuit isldeenergized for a sufficient period of time to allow relay SGGD to drop.

; The picking. up ofmake-before break contact E3 of relay? SGCD transfers the stick circuit of relay 'SGCH from to through back contact 24 of relay 2FP. When relay Z-FP is picked up this. stick circuit is deen'ergized before relay SA picks' up its contact l5, so' that relay SGGH is deenergize'dand since front contact I5 of: relay SA- is immediately closed relay- SGCH may again; be. picked up? and stuck up to store the condition that starting buttonSB' has been again actuated. 1

After the dropping of. contact l8 of relay- SGCHL the picking upof another (ED-relaysuch as relay SM'JD isprevented, even though front contact 25' of relay SM'CH is closed because the series pick-up circuit including conductor 19* is deener gized at back contact I5 of relay SA;

Assumingrelay 3Vpicked up'on thathird step, arcircuit is closed for picking up relay PC which extends from front contact ll of relay C (corresponding to: front contact 4+ of relay 0 in the above mentionedi prior application Ser. No. 640,062-) ,.back contact 43 of relay 6V, back contact 44 ofrelay 5V, back contact 45 of relay 4V, front contact 42 of relay 3V, control bus fil front contact46-of' relay- SGGD; control bus 41 and winding of relay PC, to-

The picking up ofrelay BC preselects for the.,next energization Oflihq control line, .-since the terminal of battery; CB extends through back contact 5|] of relay NC,.ffront. contact 5 of' relay PC, back contact 52 of' relay El? and windingof relay F to line conductor Ill. Relay F at the fieldstation/is positioned to the right which closes a circuit for picking. up relay lP'Cextending from (+7, front contact H8 of relay S0 contact '4 of relay F in. its right hand dotted position, b'ack contacts llll; HI and H2 of relays 6V 5V and 4V 'respectively, front contact N5 of relay"3V and winding of relay. IPC", to Relay IPC closes a stick circuitfor itself extending from (-1-); front contact N3 of relay sA yfront contact 'IIB and winding of relaylPC, to

Signal station relay SGST circuit extending from 0+); of relay lPC, back contact I20 of relay INC and winding-of'relay'SGST; to Sinc'eback contact ill of relay [PC is open throughout this cycle, relay SMST- cannot be'picked up. With relay SMST deenergized; thecircuits to the switch machine control relays ISMR" and ZSMR are maintained deen'ergized so' that these relays cannotbe operated-during a cycle for the transmission of signal controls only,

' When relays 4Vand 4V are picked up'to select the circuits for the fourth step, relay PC ispi'cked up over a front contact lll F is positioned to the left.

is again energized over a circuit which now extends through front contact 45 of relay 4V, control bus II, front contact 49 of relay SGCD and. front contact 40 of relay WCK to the control bus 41. The fourth impulse in control line I is therefore which positions contact H4 of relay F to the right, closing a circuit which now extends through front contact H2 of relay 4V and the winding of relay 2P0, to Relay 2PC picks up and closes an obvious stick circuit for itself by way of its front contact I 2I When relays 5V and 5V are picked up to select the circuits for the fifth impulse; a circuit is closed for again energizing relay PC extending from front contact M of relay C, back contact 43 of relay 6V, front contact 44 of relay 5V, control bus 8|, front contact 59 of relay SGCD, contact 56 of lever SGL in its right (east) dotted position, control bus 41 and Winding of relay PC, to At the field station, contact I I4 of relay F is actuated to the right closing a circuit for picking up relay 3PC which extends from front contact H8 of relay S0 contact I I4 of relay F in its right hand dotted position, back contact H0 of relay 6V front contact III of relay 5V and winding of relay 3PC, to Relay 3PC closes an obvious stick circuit for itself by way of its front contact I22.

When relay 6V is picked up to select the polarity of the sixth impulse in line conductor I0, a circuit is closed for picking up relay NC extending from front contact 4| of relay C, front contact 43 of relay 6V, control bus 9|, front contact 5! of relay SGCD, contact 58 of lever SGL in its right dotted (proceed) position, control bus 48 and winding of relay NC, to This causes line I0 to be energized with current of polarity at the sixth step so that relay A circuit is closed for picking up relay CL extending from front contact H8 of relay S0 contact H4 of relay F in its left hand dotted position, front contact I 23 of relay 6V front contact I24 of relay SGST and winding of relay CL, to Relay CL closes a stick circuit for itself extending from front contact I25 of relay T, back contact I26 of relay SP, front contact I27 and winding of relay CL, to

The executing circuit at the field station is effected on the sixth step when relay FP picks up and closes a circuit for picking up relay EX extending from front contact I28 of relay FP front contact I29 of relay 6V and winding of relay EX, to A circuit is now closed for positioning direction relay TD to the right extending from (3+), front contact I30 of relay EX, front contact I3I of relay 3PC, back contact I32 of relay 3NC, front contact I33 of relay SGST, conductor I34, front contact I35 of relay M and winding of relay TD, to (CN).

Since it is assumed that-track switches ITS and 2TS are in their normal lock positions, the polar contacts of relays ISMR, IWP, ZSMR and ZWP are in their right hand positions with the neutral contacts of the WP relays in their energized positions. A circuit is now closed for picking up relay front contact I36 of relay CK, conductorI31, front contact I38 of relay IWP, polar contact I39 of relay IWP in its right hand position, polar contact I40 of relay ISMR in its right hand position, winding of relay IEG, polar contact I 4I of relay TD in its right hand position, conductor I42 and front contact I43 of relay IEG which extends from CL, to Relay IEG clears signal IE by means of its contact I 44.

The picking up of back contact I45 of relay IEG opens the series energizing circuit of relay M, so that this relay is dropped and at its front contact I46 (CN) potential is removed from relays ISMR and ZSMR so that all switch control circuits are locked to prevent their energization or switch movement when a signal is cleared. The dropping of front contact I35 of relay M opens the energizing circuit of relay TD to prevent a change in the direction selecting circuit when a signal is cleared. The dropping of back contact I 41 of relay M connects to conductor I37, which provides a stick circuit for maintaining the signal clear in the event that relay CK is dropped on a subsequent cycle, for a purpose which will be later pointed out.

The, passage of an eastbound train over the detector track section in acceptance of the cleared signal IE deenergizes track relay T, which opens front contact I48 deenergizing track repeating relay I? and thereby closing back contact I49. The opening of front contact I25 of relay T deenergizes the stick circuit of relay CL so that this relay has time to drop before the closure of back contact I49 of relay 1?.

The dropping of relay CL deenergizes conductor I 42 which is effective to drop relay IEG for putting signal IE to stop. The closure of back contact I49 of relay TP prepares the stick circuit for relay CL, so that this clearing relay may be stuck up on a succeeding cycle if relay T is down. The closure of back contact I45 of relay IEG again completes the energizing circuit for relay M so that this relay picks up and places the circuits in condition for receiving and executing subsequent controls subject of course to approach locking and other safeguards ordinarily provided in a system of this type.

Having considered the manner in which code receiving relays IPC, 2PC and 3PC are picked up during a cycle of operations in accordance with the code received and the specific manner in which controls result from the execution of the signal clearing circuit for signal IE, the execution of the remaining codes may be taken up individually with the conditions established prior to the execution impulse being merely mentioned.

Other single signal clearing cgcles.For example, when signal lever SGL is actuated to its left dotted (west) position with levers ISML and 2SML remaining in their normal positions, the actuation of starting button SB initiates the cycle as before. In this event signal IW at the field station is to be cleared since it is assumed that the track switches ITS and 2TS are in their normal positions.

The operation is the same as before except that direction relay TD of Fig. 3 is positioned to the left for selecting signal relay I WG. With contact 56 of lever SGL closed in its left dotted position, the fifth stepping relay 5V selects relay NC so that the fifth impulse applied to line I 0 is for positioning relay F to the left. On the fifth stepat the field station a circuit is closed from front contact H8 of relay S0 contact H4 of relay F in its left hand dotted position, back contact I23 of relay 6V front contact I50 of relay 5V and winding of relay 3NC, to Relay 3N0 is picked up and stuck up over an obvious circuit'closed by its front contact I5I.

In this case relays IPC, 2PC and 3N0 are up when the executing impulse is applied to relay EX, so that the actuationof the contacts of relay EX closes a. circuit for positioning relay TD to'the left extending from (B), front'contact I52 of relay EX, back contact I 53'of relay 3PC, front contact I32 of relay 3NC, front contact I33 of relay SGST, conductor I34, front contact I35 of relay M and winding of relay TD, to (CN) When relay Chis picked up as previously described, a circuit is completed for picking up relay IWG which extends from front contact I36 of relay CK, conductor I3l,'front contact I38 of relay IWP, contactI39 of relay IWP in its right hand position, contact I45 of relay ISMR in its right hand position, winding of relay IWG, contact I4! of relay TD in its left hand dotted position, conductor I42 and front contact I43 of relayCL, to

The picking up of back contact I54 of relay IWG drops relay M for locking as previously described. The actuation of contact I55 of relay IWG clears signal IW as indicated .by the dotted line connection. The remainder of the operation for this condition is the same as the first detailed example and need notbe repeated.

For example, with switch. machine lever ISML already in its left dotted (reverse) position and lever SGL positioned to its right (east) dotted position, followed by theactuation of starting button SB, then the cycle of operations is similar to the first detailed example except in this case track switch ITS will be in its reverse position and relays ISMR and IWP will be actuated to the left. In this example signal IAE is to be energized to clear trafic in an eastward direction over track switch ITS reversed.

When stepping relay V selects contact 55 of lever SGL the circuit is extended to relay PC forapplying a impulse to the control line on the fifth step.

. This impulse actuates relay F to the right as before so that relay' 3P0 will be picked up. Relay TD is positioned tothe right asbefore so that a circuit is closed for picking uprelay IAEG which extends from front contact 13601 relay CK, conductor I31, front contact I38 of relayIWP, contact I39 of relay IWP in its left hand dotted position, contact I55 of relay ISMR. in its left hand dotted position, winding. of

relay IAEG, contact I51 of relay TD in its right locked positions, then the actuation of lever SGL signal IAW when track switch ZTS is normal and i TS is reverse, switch machine lever ZSML will be in its right (normalljposition and lever ISML in. its left (reverse) position. The actuaticn of leverSGL to its leftifwest) positionfollowedby the actuation of starting button SB causes the system to go through a cycle of operations as before. In this event, relay 5V's elects negative coderelay NC through contact 55 of leverSGL i'nitsleft dotted position; This makes the fifth impulse in the line circuit which positions relay F to the left for picking up relay 3N0 as previously described. Y w

Relay. 3N0 pickedup and relay 3PC down cornpletes the executing circuit for positioning relay TDto'the left when relay EX is picked up to close its front contact I52, which circuit has been previously described. With relay TD' positioned to the left, a circuit'is closed for picking upfrelay IAWG which extends from front contact I36 of relay- CK, conductor I31, front contact I38 of relay IWP, contact I39 of relay IWP in its left hand dotted position, contact I56 of relay ESMR in'its left hand dotted position, contact I59 of relayZWP in its right hand position, contact I50 of relay 28MB in its right hand position, winding of relay I'AWG, contact I51 of relay TD in its left hand dotted position, front contact I58 of'relay 2WP, conductor I42 and front con tact' I43 of relay CL," to Contact I84 of relay IAWG clearssignal IAW and contact I83 locks the control circuits as before.

For example,-if-the operator desires to clear signal IBW, signal lever SGL is operated to its left (west) dotted position and assuming that track switches ZTS and ITS are both in their reverse locked positions, and assuming that switch machine levers ISML and ZSML are in their left (reverse) positions, the system steps through a cycle as before. Since contact 56 of lever SGL is in its left dotted position, stepping relay 5V selects relay NC so that the fifth impulse applied to the line is relay 3N0 instead of relay SP0 and when executing relay EXis picked up at the end of the cycle, relay- TD is positioned to the leftas previously described. When relay CLis picked up to clear the signal, a circuit is closed for picking up relay IBWG which extends from front contact I36 of relay CK, conductor I31, front contact I 38 of, relay IWP, 'contactISSIof relay IWP in its left hand dotted position, contact I56 'of relay ISMR in its left hand dotted position, contact I59'of relay ZWP in its left hand dotted position, contact I6! of relay ZSMR inits left hand dotted" position, winding of relay IBWG, contact I 51 of relay TD in its left hand dotted position,- front contact I58 of relay 2WP, conductor I42 and frontcontact I43 of relay CL, to- Relay IBWG clears signal I BW by actuating its contact I62 and locks the controlcircuits by actuating its contact I80.

It will be noted-that the picking up of any signal clearing relay opens the series energizing circuit" of relay M for a purpose which has been already described. The passage of a train over the detector track section in acceptance of a cleared signal causes relays T and TP to be sequentially dropped, which'results in the momentary opening of the stick circuit of'relay CL so that this relay is deenergized in readiness for preparing the' next signal clearing circuit.

In the above recited examples, relay SGCD is picked up when front contact I8 of rela'y- SGCH is closed and the corresponding relay SGSTj at the field station is picked up due to the fact that thethird impulse in the line is for picking up relay IPC, as determined by relay SGCD-being up for'selecting relay P C by"way"o'f;front contact 45 ofrelay SGCDJ" Relay 2PC-is picked upon the fourth step because relay WCK remains This is effective to pick up up,'so that the fourth impulse is as selected termined by signal lever contact. 56 being in its right (east) dotted position. The combination of relay 3PC up and relay 3NC down positions relay TD to the right for selecting any eastbound signal clearing relay. With relay 3NC picked up on the fifth step, as' determined by lever SGL being in its left (west) position, the combination of relay 3NC up and relay 3190 down positions relay TD to the left for selecting a westbound signal clearing relay,

Since contact 58 of lever SGL is in either its right or left dottedpositions in the above examples, the sixth impulse is for picking up relay CL on the sixth .step to prepare the signal clearing circuit. If the signal lever contact 58 is in its neutral position, then relay PC is selected on the sixth step for making the sixth impulse which is the stop code. A impulse on the sixth step positions relay F to the right to close a circuit for picking up stop relay SP. This circuit extends from front contact II 8 of relay S0 contact 4 of relay F in its right hand dotted position, front contact IIO of relay 6V front contact I09 of relay SGST and winding of relay SP, to Relay SP opens the stick circuit of relay CL at its back contact I26 so that relay CL is dropped to put all signals to stop by deenergizing conductor I 42. Contact 56 of lever SGL in its neutral position connects to the control bus for the purpose of providing an impulse in the line at the fifth step so that the system will take this step when the stop code is transmitted.

Switch operation-In the above examples it is assumed that neither switch machine lever ISML nor 2SML are moved to a new position when a cycle is initiated to clear a signal. It will now be assumed that the switch machine levers are moved to new positions and an explanation will be given of the operation of the system.

In this case the system steps through two cycles of operations, the first cycle being effective to select and prepare the signal clearing circuits and the second cycle being effective to condition the switch machine control circuits, after which the signal clearing, circuits are completed, provided proper response and correspondence is established between the various control devices at the field station.

For example, it will be assumed that the operator moves switch machine lever ISML from the reverse position to the normal position and that lever SGL is in its right dotted position for clearing signal IE. The momentary opening of contact 32 deenergizes the stick circuit of relay WCK, which stick circuit includes front contact 33 of relay WCK, and this relay is dropped. When starting button SB is actuated, relay SGCI-I is picked to initiate a cycle of operations as previously described.

Since relay WCK is down, a circuit is closed for picking up relay SMCH extending from contact 26 of button SB, back contact 29 of relay WCK, front contact 34 of relay SGCH and winding of relay SMCH, to Relay SMCH closes a stick circuit for itself extending from back contact 36 of relay SMCD, front contact 35 and winding of relay SMCH, to Relay C is picked up to close its front contact 4| by means of circuits which are disclosed and described in the above mentioned prior application. Ser. No. 640,062. The system now steps through a cycle with the stepping relays in the control office and at the field station, illustrated in Fig. 2 operating in synchronism.

A circuit is closed through front contact I8 of relay SGCH for picking up relay SGCD as previously described. On the first step after station selection (third step) relay PC is picked up to energize the control line with a impulse. This impulse at the field station picks up relay IPC as before.

Relay 4V selects relay NC on the fourth step by Way of back contact of relay WCK, so that the line circuit is energized with a impulse which is effective to pick up relay 2NC over a circuit extending from front contact H8 of relay S0 contact I I4 of relay F in its left hand dotted position, back contacts I23 and I of relays 6V and 5V respectively, front contact of relay 4V and winding of relay 2NC, to Relay ZNC closes an obvious stick circuit for itself by way of its front contact I 64.

On the fifth step relay PC is picked up to provide a impulse in the line circuit because contact 56 of lever SGL is in its right dotted position. This causes the energization of relay 3PC at the station since relay F is positioned to the right.

On the sixth step, relay NC is energized to provide a impulse in the line circuit because contact 58 of lever SGL is in a proceed position. This picks up relay CL at the station to prepare the signal clearing circuit as previously described. In this instance, however, the signal clearing circuit cannot be completed because relay CK is dropped on the fourth step. This is because relay SGST is picked up on the third step, since this is a signal clearing cycle and because relay 2N0 is picked up on the fourth step due to a switch machine lever having been moved to a new position. With relays SGST and 2NC picked up, the stick circuit of relay CK is deenergized at back contacts I65 and I66 of these respective relays. Since potential is removed from conductor I 31 by the dropping of contact I36 of relay CK, the signal clearing circuit is incomplete. At the end of this cycle relay EX is actuated to close the previously described circuit for positioning relay I'D to the right due to the fact that relay 3PC is picked up and relay 3NC remains down.

Relay SGCD in the control office is dropped at the end of this cycle as before. Relay SMCD is picked up over a circuit extending from back contact I5 of relay SA, back contact I6 of relay NC, back contact I! of relay PC, back contact I8 of relay SGCH, front contact 25 of relay SMCH and winding of relay SMCD, to Relay SMCD closes a stick circuit for itself through its front contact M which is similar to the previously described stick circuit for relay SGCD.

Since relay SMCH is picked up, its front contact 28 causes the system to be initiated into a second cycle of operations. On the third step of this cycle relay NC is picked up by way of a circuit including front contact 31 of relay SMCD so that the line is energized with a impulse. At the field station, relay F is actuated to the left for picking up relay INC over a circuit including front contact II9 of relay 3V Relay INC closes an obvious stick circuit for itself by way of its front contact I61.

On the fourth step relay PC is energized over a circuit including front contact 38 of relay SMCD and contact 39 of lever ISML in its. right position. This energizes the line with a impulse so that relay 2PC at the field station is energized over a circuit including front contact I I2 of. relay lv iand' contact I of relay F in its right hand dottedpositionw r; v I

On the fifth step relay PC is energized over a circuit 1 including front contact 60- of relay SMGD :and contact 62 of =lever-2SMLin its right I positionr This energizes the control line with a impulse so that relaySPC is picked-up over a circuit including front contact I II of relay 5V and contact H4 of'relay F in its right hand dotted position. 1

n the sixthstep a circuit-is closed for picking up relay NC by way of front contact 63 of relay llb " lay IPC is down and relay INC is up during this cycle, relaySGST'is deenergized; Relay SMST is energized over a circuit extending from; front contact IZIIofreIay-lNQ'backcontact II! of relay IPO and Winding of relay SMST, to r ReIay EX is picked up at the end of this second cycle-and a circuit is closed for picking up relay CKwhich extends from front contact I68 -of relayEX; front-contact 169 of relay SMSTandwinding of relayCK; to Relay CKestablishes astick circuit-for itself extending-fromback contact 1650f relay SGST, front-contact I'm-and winding of relay OK; to r Recallingthat relayCL was picked'up at *the enctof the first cycle and sincerelay CK-is picked up at the end of the second cycle, conductors I31 and l42 are both energized so that signal IAE may becleared as soon as the switch machine control and repeating relays are in proper correspondences 4 The picking up of relay EX closes a circuit for positioning relay ISMRto its right hand position which extends from -(B+),' front contact I3llof relay front contactJ'IB of=relay- 2PC back contact 112 of relay.-2NC,"frontncontact I13 of relay 2 SMST; conductor 114,- winding of relay ISMR and. front contact. I46 of relay M; to .(CN). v Since relay .3PC is pickedup andsince relay 3NC :is down, a circuitis also closed for energizing relay 28MB extending from (B+-); front contact I30 of .relay EX, front contact I3lof relay 3PC, back contact I32 of relay3NC, front contactill of relay SMST, conductor 116; Winding of relay ZSMR and front -contact-I46-cfrelay M, Eto (CN) Since it was 'assumedthat lever ZSMLwas already in its right (normal) position, relay ZSMR. is in its right hand position at this timeso that the-energization of its winding does not shift its contacts. 1

Relay I SMR closesacircuit (notshown) *for energizingxthev switch machine motor over-its normal operating circuitaand when relay-1W1 responds bypositioning its polar contact I39zto the right andby pickingoup its.neutral contact I38 as an indication that trackmswitch .ITS is in its normal; locked positioni. the. circuit gforrelay .lEG is completedw This circuit extends from (+9, front contact 136 of relay CK, conductor. I,.3'I ,front contact; :I 38 got .renmwra. contact I 39 Relay INC up of relay 1 WP inits right hand position, contact 140 of relay ISMR" in;- its; right hand position, winding of: relay IEG, contact l 4 I of relay TD in its right hand:position,.conductor I42 and front contact- I43of relay CL; to Signal IE is cleared and the control circuits are looked as previously described.

' Consideration of other combinatz'mta-The description above more specifically-points out the transmission: of -:two code combinations during two cycles-formoving track switch ITS from reverse to normal, leaving track switch ZTS in its normal position and clearing signal IE, Any one of the other signals maybe similarly cleared in response tothe transmission of the proper code combinationsas applied to the linecircuit in the control ofiice by the corresponding combinations set up by the switch machine and signal levers.

For example, assuming that lever ISML is movedfrom-its left (re-verse) to its right (normal) position, lever ZSML is left in its normal position and lever SGL positioned inits left dotted (west) position, then signal 'IW will be cleared for a train to-advanceover the maintrack'in a westbound direction. In other words, track switch .I'IS willbe moved toits normal position, track switchZTSwill remain in its normal position and signal IW will be cleared. Duringthe operation of the first cycle under this condition, code receiving relays IPC, 2N0 and 3NC will be picked up on-steps 3; 4 and 5 respectively. This is determined in the control olfice by relay PC being selectedon the third step through front contact lfi of relay-SGCD, relay NC being select'edon the fourth step through front contact of relay-SGCD,-and' back contact 40-of relay WCK and relay NC being selected on thefifth step through front contact 59 of relay SGCD and contact 56-of lever SGL inits left position.

On the sixth step relay CL at the field station is-picked up as previously described' and-stuck up until =the-track section becomes occupied or until a stop signal is transmitted. This is brought about by relay 6V in the control office selecting relay NC through front contact 51 of relay SGCD and contact 58 of lever-SGL in its proceed posi-- tion; Relay TD at the field/station is positioned to the left as previously explained, since the circuit extends to (B) at front contact I52 of relayEX'by way ofback contact I53 of relay 3P0, front contact I32 of relay 3N0 and front contact I33 oflrelay SGST; Relay SGS'I is picked up during the first cycle; because relay IPC is up.. This operation .hascbeen previously described;

. During thesecond'zcycle relays INC, 2P6 and 3P'C will. be picked up at the field station as .determinedby the-selecting circuits through front contact 31- of relayfSMGDonthe third step,'front contactl38 of relay SMCD and contact 39 oflever ISML in its right position on the fourth step and front contact :60 of relay SMCD and contact 62 of lever ZSML in its right position on the fifth step. r I F and relay- IPC down drops relay SGST'and'picks up relay SMST to mark this as a second.-- cycle."' At the end of the second cycle .the previously I described executing circuit picks uprelay'EX-and closes acircuit from (B-F). at front contact I30 of relay EX,- front contact l-l9-offrelay 2P0; back contact N2 of relay ZNC, front contact I'ISJQfIeIay SMST, conductor I14, winding of, relay ISMR and-frontcontact-l lfi of relay lvL'to .(CNT). This positions relay ISMR to the right for positioning track switchITS to normal. Since relay 2SMR isjassumedl to be already in its normal position, track switch 2TS will be in a corresponding position;

Of course, it will be understood that relay CK was dropped during the first cycle and picked up at the end of the second cycle, so that the signal vclearing circuit is .not completed until the end of the second cycle. This circuit extends from front contact I36 of relay CK, conductor I31, front contact I38 of relay IWP, contact I39 of relay IWP in its right hand position, contact I40 of relay ISMR in its right hand position, winding of relay IWG, contact I4I of relay TD in its left hand position, conductor I42 and front contact I43 of relay CL, to Relay I WG is picked up to clear signal IW and to-drop relay M which looks the switch machine control circuits as before.

For example, assuming that lever ISML is moved from its, normal to its reverse position, that lever ZSML stays in its normal position and lever SGL is actuated to its right (east) dotted position, relays IPC, 2NC, 3PC and CL will be picked up on steps 3, 4 5 andfirespectively. This combination of relays is determined by relay SGCD being up on the third step, relay WCK being down on the fourth step, lever SGL being in its right dotted position on the fifth step and contact 58 being in its actuated (proceed) position on the sixth step.

Relay IPC up and. relay INC down selects and operates relay SGST. Relay 2NC picked up with relay SGST picked up drops relay CK. Relay 3PC up and relay 3NC down completes a circuit from (B+), through front contact I30 of relay EX, front contact I3I of relay 3PC and back contact I32 of relay 3NC for actuating relay TD to the right. v j

During the second cycle relays INC, 2NC and 3PC will be pickedup on steps 3, 4 and 5 respectively as determined by relay 3V in the control ofiice selecting relay NC through front contact 31 of relay SMCD, relay 4V selecting relay NC through contact 39 of lever ISML in its left dotted position and relay 5V selecting relay PC through contact 62 of lever 2SML in its right position. When relay EX is picked up to execute this combination, relay ISMR-is actuated to its left hand position because the circuit from'(B-) at front contact I52 of relay EX is established by way of back contact I1I of relay 2PC, front contact I12 of relay 2NC and front contact I 13 of relay SMST. Relay 2SMR is energized with (B+), since the circuit through front contact I30 of relay EX is extended through front con-. tact I3I of relay 3P0, back contact I32 of relay 3NC and front contact I15 of relay SMST. The signal clearing circuit is established for clearing signal IAE by picking up relay IAEG over a circuit including contact I51 of relay TD in its right hand position, contacts I56 and I39 of relays ISMR and IWP in their left hand dotted positions. c

For example, assuming lever ISML moved from its normal to its-reverse position with lever 2SML remaining in its normal position and lever SGL actuated to its left (west) position, then relays IPC, 2NC, 3NC and CL at the field station will be picked up during the third, fourth, fifth and sixth steps respectively. This is because the third step in the control office selects relay PC through front contact 46 of relay SGCD, the. fourthstep selects relay NCbecause contact 40 of relay WCK is dropped, relay 5V selects relay NC because lever SGL is in its left (west) position and relay 6V selects relay NC because lever SGL is in a proceed position;

Relay IPC up and relay INC down picks up relay SGST to mark this as the first cycle for preparing the signal clearing circuits. Relay 2N0 picked up with relay SGST up drops relay CK toprevent clearing a signal until another cycle is transmitted. Relay 3NC up and relay 3P0 down positions relay TD to the left (west) over the previously described circuit including front contact I52 ofrelay EX.

The system now advances through its second cycle when relays INC, 2NC and 3PC are picked up. This is because relay NC in the control office is selected on steps 3 and 4 through front contacts 31 of relay SMCD and front contacts 38 of relay SMCD and 39 of lever ISML in its left dotted position respectively. Relay PC is selected on the fifth step through contact 62 of lever ZSML in its right position. Relay SGST is dropped and relay SMST is picked up (at the field station) at the start of'the second cycle as previously described and when execution is effected at the end of the second cycle, relay ISMR is positioned to the left over a circuit extending from (B), front contact I52 of relay EX, back contact I1I of relay 2PC, front contact I12 of relay 2N0, front contact I13 of relay SMST and over the remainder of the previously described circuit.

Relay ZSMR is energized with current of the proper polarity for maintaining this relay in its right hand position over a circuit extending from (3+) front contact I30 of relay EX, front contact I3I of relay 3PC, back contact I32 of relay 3NC.and front contact I15 of relay SMST over the remainder of the previously described circuit. Since relay TD is positioned to the left a circuit is completed for picking up relay IAWG extending from front contact I36 of relay CK, conductor I31, front contact I38 of relay IWP, contact I39 of relay IWP in its left hand dotted position, contact I56 of relay ISMR in its left hand dotted position, contact I59 of relay 2WP in its right hand position, contact I60 of relay ZSMR in its right hand position, winding of relay IAWG, contact I51 of relay TD in its left hand dotted position, front contact I58 of relay 2WP, conductor I42 and front contact I43 of relay CL, to Relay IAWG clears signal IAW and locks the control circuits as previously described.

For example, assuming lever ISML moved from its normal to its reverse position with lever ZSML in its reverse position, then relays IPC and ZNC are picked up on the third and fourth steps of the first cycle for reasons previously explained. Likewise, relay SGST at the station is picked up and assuming lever SGL in its right dotted position, relay PC is picked up on the fifth step which makes the fifth impulse in the line (-i-) for picking up relay 3P0. In the event that lever SGL is in its left position, then relay NC is picked up for making the fifth impulse in the line circuit which picks up relay 3NC.

With relay 3PC up and relay 3NC down (lever SGL in'its east position), the execution circuit closed at the end of the first cycle extends from (B+) through front contact I30 of relay EX, over the previously described circuit to relay TD for positioning-this relay to the right. With relay 3NC up and relay 3PC down (lever SGL in its west position), then the executing circuit for relay I'D at the end of the first cycle extends from (B) through front contact I 52 of relay I13 of relay SMST.

EXover the previously described circuit .to relay During the second cycle under these two conditions, relays INC, 2NC and 3NC are pickedfup as determined by relay SMCD having its front contact 31 closed, lever ISML having its contact 39 closed in the left dotted positionand lever 2SML having its contact 52 closed in its left dotted position. At the end of the second cycle the executing circuit is effective to position relay ISMR to the left (reverse) because the circuit is completed to (B) at front contact I52 of relay EX by way of back contact H! of relay 2PC, front contact I12 of relay 2N0 and front contact (B-) is also applied to relay 2SMR from front contact I52 of relay EX by Way of back contact I53 of relay 3P0, front contact I32 of relay 3NC and front contact I15 of relay SMST.

The signal clearing circuits with the switch machine control and repeating relays in their reverse positions is established through relays IAEG or IBWG as determined bythe position of polar contact I51 of relay TD. Relay IAEG will be picked up to clear signal IAE if contact I51 of relay TB is in its right hand position (east) over a circuit extending from (B-l-j) front contact. I36 of relay CK, conductor I31, frontfcontact I38 of relay IWP, contact I39 of relay IWP in its left hand dotted position, contact I56 of relayISMR in its left hand dotted position, winding of relay IAEG, contact I51 of relay TD in its right hand position, front contact I53 of relay 2WP, conductor I42 and front contact M3 of relay CL, to

The circuit for relay IBWG which clears signal IBW extends from (B-|-), front contact I36 of relay CK, conductor I31, front contact I38 of relay IWP, contact I39 of relay IWP in its left hand dotted position, contact, I56 of relayISMR in its left hand dotted position, contact I59 of relay 2WP in its left hand dotted position, contact I6I of;relay ZSMR in its left hand dotted position, winding of relay IBWG, contact I51 of relay in its left hand dotted position and over the remainder of the previously. described circuit, to g In the above examples describing the operation when a switch machine lever is moved to a new position, it has been explained that relay WCK is dropped when its stick circuit is momentarily opened by contact 32 or 12 of lever ISMLor ZSML. At the end of a second cycle, relay WCK is picked up when relay SA is dropped-and before relay 2SA drops over a circuit extending from back contact 230i relay SA, front contact 64 of relay ZSA, front contact 65 of relay SMCD and winding of relay WCK, to Relay WCK is then stuck up until the next actuation of a switch machine lever.

It has also been explained how the code receiving relays IPC, 2PC, 3P0, INC, ZNC and 3N0 are picked up in various combinations and are stuck up. It will be understood that the stick circuit of these relays is deenergized at the end of each cycle when relays 6V and SA are down, opening their front contacts I03 and H3 respectively. It will be obvious that thestop code (that is, on thesixth step) is effective when. a switch machine lever has been moved to, a new position because on the sixth. step of the firstpycle picks up relay SP which prevents relayCL being up to clear any signal in,..the second cycle.

m er The system lof -the present invention provides such false operation might happen.

for the checking and clearingof routes over a plurality of railway track switches at a single station together-withthe putting'to stop of any of these routes by means of combinations of route control codes transmitted over a selective deenergized positions. One or the other of the code receiving relays for the corresponding step must receive its impulse in order for a code to be transferred from the code receiving relays to the function control relays at the end of an operating cycle.

I It will be apparent from the drawings and description that if for some reason neither code receiving relay for a particular step is picked up or if both are picked up the executing impulse at the end of the cycle will beineffective to energize either station relay to position the traffic direction control relay or to position the switch machine control relays depending upon the step at which In. other words, the controlcircuits are dependent upon the proper energization of the code receiving relays sothatan open or ashort circuit preventing the response of either or resulting in the response of both does not cause improper control operation. V

This means that a surge in the line which may iii) effect the picking up of a PC relay (see Fig. 2) v at a particular step when the code impulse picks up the corresponding NC relay of that'step and Vice versa, or the loss of an impulse resulting in the failure to pick up either a PC or an NC relay at a particular step, results in the failure'to complete the executing circuit for changing a existing switch position" or signal condition.

For example, if relays IPC and INC should both (or neither) be picked up, neither relay CL nor relay SP can be energized to clear ajsignal or put an existing cleared signal to stop, because relay SGST' cannot be energized under this condition. Since relay SMST cannot be pickedup, neither switch control relay ISMR nor ESMR can be energized.

For example, if relays 2PC and 2NC should both (or neither) be picked up, the executing circuit extending through contact I52 of re1ay=1- EX is left open either at contact I1I of'relay 2P0 or contact I12 of relay-2NC. Likewise thev executing circuit extending through contact I of'relay EX is left open either at contact I19 of relay EX is leftopen either at contactI3I of relay 3P0 or. contact I32'of relay3NC.

Also, the circuits are so arranged that the switch control relays may not be operated to new positions while a signalis clear asgoverned by the series circuit of relay M-controlled by the signal clearing relays. a i Y Another feature of the present invention resides in the manner in which signals may be cleared during a single operating cycle of the communication system by transmitting a code combination of one class,-as determined by the condition that no switch machine control lever in the office is moved to a new position. Two operating cycles are requiredto clear a signal. when a code combination of a second class is transmitted, as determined by the condition that a switch machine control lever in the oifice is moved to a new position.

Another feature of the present invention resides in the manner inwhich the signal clearing circuits are prepared but not completed during the first cycle when the communication system advances through two cycles of operation as a result of a switch machine lever being moved to a new position. In this event, the switch control circuits are completed during the second cycle and at the end of this cycle the proper signal is cleared subject to proper response and correspondence of the control circuits of both cycles.

Having thus described a centralized trafiic controlling system as one specific embodiment of the present invention, it is desired to be understood that the present form is selected to facilitate in the disclosure rather'than to limit the scope of the invention and it is to be further understood that various modifications, adaptations and alterations may be made in the present disclosure to meet the requirements of practice without in any manner departing from the spirit or scope of the present invention except as limited by the appended claims.

What I claim is: 1. In a centralized traffic controlling system, control oilice, a field station, a control level in said office, a signal at said station, a line circuit connecting said oflice with said station, a clearing relay and a checking relay at said station, means controlled over said line circuit for momentarily closing pick-up circuits for said relays, a stick circuit for said clearing relay controlled by track conditions at said station, a stick circult for said checking relay controlled by a change in the position of said lever, means jointly controlled by said relays for clearing said signal subject to traflic conditions, and means. for thereafter maintaining said signal clear irrespective of the condition of said checking relay, 7

2. In combination, a track switch and a plurality of signals for governing trafiic over said track switch, a line circuit having a plurality of series of code impulses of different classes transmitted thereover for controlling said track switch and said signals, code receiving relays each responsive to an impulse of said series for receiving and storing said series of impulses, means effective after the reception of a series of impulses of a first class for clearing one of said signals, means responsive'to the reception of a series of impulses of a second class for clearing one of said signalsonly after the reception of a series of impulses of a third class, and means responsive to a series of impulses of a third class for controlling said track switch.

3. In a normally at rest'code type selector system, a plurality of switch control levers, a signal control lever, a starting button, means initiating the communication system into a single cycle of operation to transmit a signal control code in accordance with the position of said signal control lever upon the momentary actuation of said button provided all of said switch control levers have not been moved, and means initiating the communication system into a plurality of cycles of operation for transmission of both switch and signal control codes upon momentary actuation of said button if one of said switch control machines has been moved to a new position.

4. In a centralized traffic control system of the character described, the combination with a power-operated track switch and signals at a field location for governing train movement over said switch in its different positions, of switch control means at the field location for governing said switch, a clearing circuit for each signal closed only if said switch is in a position corresponding with its control means, a switch lever and a signal lever in the control office, a code communication system for transmitting signal control and switch control codes on difierent operating cycles in accordance with the position of said signal lever and switch lever respectively, means operating upon movement of said switch lever to a different position for modifying the signal control code, and means at the field location rendered effective by the transmission of a signal control code so modified for opening the signal clearing circuits for all of said signals until a switch control code is subsequently received to actuate the switch control means.

5. In a centralized traffic control system of the character described for controlling the Operation of a plurality of track switches and signals governing train movement over said switches. comprising, a plurality of manually operable switch levers in a control oflice one for each of said switches, a signal control lever in the control oflice, a communication system of the code type for transmitting on different cycles switch con- 2 trol and signal control codes in accordance with the positions of said switch control and signal control levers respectively, means responsive to the movement of any one of said switch levers to a different position for changing one code element of the signal control code to a particular character, a stick relay at the field location which mustbe energized to permit clearing of any of said signals, means in the field for momentarily opening the stick circuit of said stick relay upon reception of a signal clearing code having one element thereof changed to said character, and means responsive to the reception of a switch control code for closing a pick-up circuit for said stick relay.

6. A centralized trafilc control system for governing from a distant control ofiice by a code transmission system, the position of a plurality of track switches and signals governing train movement over said switches comprising, manually operable switch control levers one for each switch located in the control office, a signal control lever in the control ofiice, a communication system of the code type for transmitting during one operating cycle a switch control code in accordance with the existing position of said switch levers and during another cycle a signal control code dependent upon the position of said signal lever, means responsive to the movement of any one of said switch levers to a difierent position for modifying in a certain respect the signal clearing code, and means at the field location rendered effective by the reception of a signal clearing code modified in said respect for preventing clearing of a signal until a switch control code is subsequently received.

7. In a centralized traffic control system of the character described for controlling a track switch and signals governing train movement over said switch in its diflerent positions, a switch lever,

a signal lever, a normally at rest communication system of the code type for governing operation of said switch during one operating cycle in accordance with the position of said switch lever and for governing the clearing of said signals during another cycle in accordance with the-posi tion of said signalilever, means in the control oflice for modifying the signal control code trans mitted whenever: saidswitch lever is moved to, a, diiferent. position, means at the field. location rendered effective by the transmission. of a signal control code of said modifiedcharacter for preventing clearing of a signal until a newrswitch control code is subsequently received, and manually controlled means in the control oflice for initiating said communication and causing it to transmit a modified signal control code dur-l ing one operating cycle and a switch control code during a subsequent operating cycle. I

8. In a system of the character described, a

plurality of power-operated track switches and signals governing train movement over said switches to be controlled from a distant control ofilce, switch control meansfor each switch, a communication system of the code type operable during a switch control cycle to govern said switch control means for all of said switches, clearing circuits for said signals, said clearing circuit for a given signal being closed only if all of said switches and their respective switch control means are in corresponding positions to provide a route for train movement governed by such signal, and means at the field location controllable from the control office over said communication system for opening and maintaining open said clearing circuits for all of said signals until all of said switches are subsequently controlled during a switch control cycle.

9. In a centralized trafllc controlling system for railroads; a field station having a track switch and signals for governing trafiic thereover; a control office having a manually operable switch control lever and a manually operable signal control lever; a communication system of the multiple impulse code type for transmitting during one cycle of operation a signal control code in accordance with the position of said signal control lever and the changed condition of said switch control lever, and for transmitting during another cycle of operation a switch control code in accordance with the position of said switch control lever; a clearing relay and a checking relay at said station; a stick circuit for said clearing relay controlled by track conditions at said station; a pick-up circuit for said clearing relay closed upon the reception of a signal control code transmitted with said signal lever in a clearing position; a stick circuit for said checking relay opened upon the reception of a signal control code transmitted following a change in position of said switch control lever before the transmission of a switch control code; a pick-up circuit for energizing said checking relay upon the reception of a switch control code; circuit means for clearing the said signal only when said clearing relay and said checking relay are both energized; and circuit means rendered effective once a signal is cleared for maintaining such signal in a clear condition dependent upon the energized condition of said clearing relay but independently of thecondition of said checking relay.

10. In a centralized trafiic controlling system for railroads; a field station having a track switch and signals for governing traflic thereover; a control oifice having a manually operable switch control lever and a manually operable signal control lever; a communication system of the multiple impulse code type for transmitting difierent control codes from the control ofiice to the field station; circuit means in the control office for causing said communication system to transmit a signal clearing code with said'signal lever in a clear position and said switch lever in an unchanged position since the last transmission of a switch control code, said means causing said communication system to transmit a modified signal clearing code if said switch control lever has been changed in its position since the last transmission of a switch control code; circuit means in the control office for causing saidcommunication system to transmit a switch control code in accordance with the normal or reverse position oi? said switch control lever following the transmission of every modified signal clearin code transmitted; code receiving means at said station responsive to the reception of a signal clearing code for immediately clearing said signal and responsive to a modified signal clearing Code for clearing said signal only after the reception of a switch control code at said station; and code receiving means at said field station responsive to a switch control code for operating said track switch to a position determined by the position of said switch control lever; whereby the reliability of the code type communication system is checked so as to allow the clearing of a signal after a switchlever movement only provided a switch control code is received at the field station.

11. In a centralized traific controlling system for railroads; a plurality of track switches at a field station; a control oifice having a plurality of manually operable switch control levers one for each of said track switches; a communication system of the multiple impulse code type for transmitting different codes from the control of fice to the field station on difierent cycles of operation; circuit means for causing said communication system to transmit a particular code on one cycle of operation if any one or several of said switch control levers has been operated to diiferent positions; other circuit means causing said communication system to transmit on another cycle of operation a switch control code characteristic of the positions of said switch control levers, said another cycle of operation following said one cycle of operation; code receiving means at said field station responsive to said particular code; other code receiving means at said field station responsive to said switch control code for controlling said track switches to positions corresponding to their respective switch control levers; signals at said station for governing trafiic over said track switches; and circuits for at times clearing said signals, said circuitsbeing closed only after both said code receiving means have responded to their respective codes.

12. In a centralized traflic controlling system of the character described; a field station having a track switch and signals for governing trafiic over such track switch in its difierent positions; a control ofi'ice having a manually operable switch control lever operable to normal and reverse positions and a manually operable signal control lever operable to clear or stop positions; a. communication system of the multiple impulse code type connecting said control oflice and said field station for transmitting difierent codes; signal circuit means at the control ofiice for causing said communication system to transmit a signal clearing or signal stop control code on one operating cycle of said communication system depending upon the position of said signal control lever; switch circuit means effective to cause said communication system to transmit a normal or reverse switch control code on another cycle of operation of said communication system in accordance with the normal or reverse posit-ion of said switch control lever; means including a stick relay efiective to modify a signal control code irrespective of whether it is a clearing or stop code; a normally closed stick circuit for said stick relay momentarily opened upon each movement of said switch control lever to a difierent position; a pick-up circuit for said stick relay closed momentarily upon the transmission of each switch control code; means at the field station responsive to the reception of a signal clearing or stop control code for clearing said signal or causing it to go to stop, said means acting in response to a modified signal clearing code to clear said signal only after the reception of a switch control code at said station, and means at said station responsive to a normal or reverse switch control code for operating said track switch to a corresponding normal or reverse position.

13. In a centralized trafiic controlling system for railroads; a field station having a track switch and signals for governing trafiic thereover with an associated detector track section; a control ofiice having a manually operable switch control lever having normal and reverse positions and a manually operable signal control lever having clear and stop positions; a communication system connecting said control oflice and said field station, said system being of the code type for transmitting switch and signal control codes on separate cycles of operation; circuit means for causing said communication system to transmit a switch control code in accordance with the position of said switch control lever on one cycle of operation and to cause the transmission of a signal control code in accordance with said signal lever on another cycle of operation, said means being effective to modify said signal clearing code if said switch control lever is moved to a new position subsequent to the last transmission of a switch control code; a signal clearing relay and a checking relay at said station; a pick-up circuit for said signal clearing relay closed upon the reception of a signal clearing code irrespective of whether such signal clearing code has been modified or not; a stick circuit for said signal clearing relay closed dependent upon the condition of occupancy of said detector track section so as to be opened upon the entrance of a train into such detector track section; a pick-up circuit for said checking relay closed upon the reception of each switch control code; a normally closed stick circuit for said checking relay momentarily opened upon the reception of a modified signal control code; and circuit means including front contacts of said signal clearing relay and said checking relay for clearing said signal.

NEIL D. PRESTON. 

